This invention relates to a cushion support element for incorporation in a structure such as a seat, more especially a vehicle seat, a bed, or the like.
In the construction of seats, a particularly simple and effective form of sprung cushioning is provided by a cushion supporting platform suspended from the seat frame by means of formed wire tension springs and over which is supported a layer of synthetic plastics foam cushioning material, for example polyurethane foam. The supporting platform should be at least partly flexible, and previous proposals for the construction of such a platform include rubber diaphragms and wire lattice or metal mesh constructions.
One such construction of platform element that has proved successful is that described in U.S. Pat. No. 3,367,648. This comprises two paper wrapped side edge wires between which extend a plurality of transverse parallel wires formed of tempered spring wire such as piano wire. The transverse wires are wound around the edge wires and by deformation of the paper wrapping become interlocked therewith to maintain their relative spacing. In addition, the element may include one or more longitudinal twisted paper cords extending parallel to the side edge wires, the transverse wires penetrating the paper cord and thus being located thereby.
The above construction has the advantages of simplicity and relative cheapness, and is also very convenient to suspend in a seat frame, since formed wire tension springs may simply be anchored at one end to the seat frame and hooked at the other over the side edge wires, as described in British Patent Specification No. 1,193,065.
In such a construction of platform element, the ends of the transverse wires are wound around the side edge wires and are then bent approximately at right angles to hook over upon themselves. This arrangement, owing to the self-interlocking effect provided by the hooked ends of the transverse wires positively prevents unwinding of the wire ends under the load placed upon the seat and has proved very effective in current use. However, a drawback of the construction is the difficulty of forming the spring wire of which the transverse wires are made in such a manner as to ensure a tight connection at the side edge wires. Tempered spring wire is difficult to deform by mass-production techniques and it is not therefore possible to employ the conventional wire knots applicable to more malleable wire such as is used for example in wire netting or fencing wire. For this reason, at their point of engagement with the side edge wires, the transverse wires do not fully encircle the paper wrapped side edge wires and there is a loose connection which allows relative angular movement of the side edge wires and the transverse wires and gives the impression of a poor quality product. Moreover the projecting end of the wire hook presents a snag upon which the hands of an operative assembling a seat structure may be caught and injured, or upon which a suspension spring may unintentionally become hooked. The projecting end also tends to abrade against adjacent cushioning material of the seat, when in use, which in some circumstances may lead to unacceptable deterioration of the seat.